About one third of the adult population in the USA and other countries experiences frequent difficulty in falling asleep, staying asleep or both, and wakes up unrefreshed despite the opportunity for adequate sleep. Nearly 10% of the US population suffers from chronic sleeplessness, called insomnia. Sleeplessness may result in impaired cognitive, emotional, social and physical functionality during daytime with increased risk for accidents, lower job performance and decreased quality of life. According to analysts, Americans spent over $30 billion in 2012 on sleep-related aids.
Current methods for alleviating the problem include sleep pills, which frequently elicit side effects, improving sleep habits, controlling or eliminating negative thoughts and applying relaxation techniques for stress reduction. However, these do not appear to provide interventions that are efficient in restoring the normal falling-asleep process when disturbed.
The normal falling-asleep process involves progressive disconnection from the environment and decline in control over mental activity and awareness of sensory stimuli. During this process sympathetic neural activity is decreased with resulting muscle tone relaxation; respiration undergoes a series of characteristic variations including respiratory instability, which reflects the intermittency between the different systems that control respiration in the awake and sleep states that changes into highly regular and low-amplitude respiration.
A method and system for sensor-controlled interactive guiding of a user from normal- to slow respiration rates with modified respiration pattern has been described by the present inventor in U.S. Pat. Nos. 5,076,281 and 5,800,337. This technology was implemented in a medical device sold under the name RESPeRATE™ that guides the inspiration and expiration of its user by musical tones, with which the user is requested to synchronize (‘sync’) breathing movements. The device has been demonstrated to reduce neural sympathetic activity and was cleared by the FDA for treating stress and hypertension. However, the use of that technology for sleep induction is limited by the very process of falling asleep: with increasing drowsiness the user ability to sync breathing movements with a guiding stimulus gradually decreases and the resulting stimulus, now perceived as de-sync, frequently wakes up the user. Furthermore, user awareness regarding the quality of performing the guided respiration is important for achieving outcomes associated with the reduction of sympathetic activity that also includes falling sleep. The prior art discloses neither the detection of the awake-to-sleep transition using a measure for awareness combined with respiration characteristics during guided breathing, nor a strategy for modifying the stimulus after such detection, in a way that would not interfere in the falling-asleep process. In addition, the prior art does not provide a satisfactory real-time continuous measure for the performance quality of guided respiration. Thus, it may be desirable to improve known methods and systems in a way that would extend their applicability to sleep induction and other applications aiming to reduce sympathetic activity.